Individual magnet with adjustable sleeve pickup device



Sept. 30, 1952 H. DE ARMOND 2,612,541

INDIVIDUAL MAGNET WITH ADJUSTABLE SLEEVE PICKUP DEVICE Filed May 10, 1950 INVENTOR. Harr 0e Armand H 7" TOIPNE Y Patented Sept. 30, 1952 INDIVIDUAL MAGNET WITH ADJUSTABLE SLEEVE PICKUP DEVICE Harry De Armand, Toledo, Ohio, assignor to Rowe Industries, Toledo, Ohio Application May 10, 1950, Serial No. 161,242

6 Claims.

The principal object of the present invention is to provide an extremely simplified arrangement in an electromagnetic pick up device for individually varying the amplitud of the reproduction of the various strings of a stringed musical instrument.

The object is to provide a simple construction for the adjustability of the magnetism of each individual magnet in which, in the specific embodimentof the invention herein illustrated, a telescoping soft iron sleeve may be moved toward and away from the strings of the instrument in contact with a magnet, one for each string of the musical instrument, and spring means are interposed between one end of the magnet and the closed end of the sleeve to tension the friction and keep the magnet and sleeve held in proper adjusted position for producing the desired results.

Further objects and advantages are within the scope of the invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which maybe preferred, in which:

Figure I is a fragmentary view of a musical instrument to which the pick up device has been applied;

Figure II is a top view of the pick up device;

Figure III is a section taken substantially along the line IIIIII of Figure II;

Figure IV is a section taken substantially along the line IV-IV of Figure II;

Figure V is a perspective view of the pick up device; and

Figure VI shows individual views of the magnet, sleeve and spring.

Referring to the drawings, I provide a metal box-shaped frame III of suitable metallic material for receiving an oblong-shaped insulating block I2 for the coil form where it will be seen that the same is recessed at I3 to receive the winding I4. A top I5 of insulating material extends over the winding at the periphery thereof and also flush with the sides of the box frame Ill,

It will be seen that each end of the box frame It is left open and an extension of the base II is provided with a cutaway slot I6 so that the device may be fastened in the musical instrument by a simple expedient of screws as shown in Figure I, the heads of which may overlap the sides of the slot I6 of theframe extensions. The frame I0 and the coil form block, I2 are connected as shown by screw bolts I9 at each corner of the base, the nuts thereof being set in recesses across each end of the block I2.

I provide a plurality of transverse screw threaded openings II extending transversely of the from any one string.

block of insulating material forming the coil form I2, said openings also extending through the cover I5, there being one transverse opening I! to receive a magnet I8, for each of the strings of the instrument as shown in Figure III. These magnets are centered as accurately as possible under each string. The individual relatively permanent magnets I8 are located at the lower portion of each opening II, as shown, with the bottom of the magnets adapted to rest on the bottom of the imperforate base plate II of the box frame I0. Interposed between each magnet I8 and the insulating block I2 is a soft iron telescoping sleeve 20 screw threaded on the outside to fit into the screw threads in the openings I! of the coil form, the inside diameter of the sleeve 28 having a close fit over the outside surface of each magnet It to contact therewith. The upper end of each sleeve 20 is closed as at 2| and is also provided with a slot 22 so that the sleeve may be adjusted with a screw driver. An important feature of my invention is to localize the magnetic flux produced adjacent each respective string of the musical instrument to which the microphone is applied, the adjustability providing for the variation in the amplitude reproduced Interposed between the upper end of each magnet I8 and the closed end 2I of the sleeve is a compressed coil spring 24 adapted to normally aid in retaining the magnets in the lowermostposition as shown and provide a tension for increasing the frictional contact between the screw threads on the sleeve 20 and the screw threads in the opening II.

It will be noted that each telescoping sleeve forms a pol piece 20 which slides over each magnet but is in continuous contact therewith, and by having the screw threaded connection from the sleeve on the outside thereof withthe holesin the coil form, it is unnecessary to make any connection with or manipulate the individual magnet pieces I8, and these can be formed of short pieces cut from cylindrical stock of magnet material.

In the particular embodiment illustrated herewith, I make the casing III of soft iron to thereby facilitate the concentration of the magnetic flux in cooperation with the magnets I8 to provide a microphone pick up in which the magnetism may .be localized as much as possible.

In operation, any one of the sleeves 20 may be adjusted by the musician, as desired, to obtain a balance or other effect in the amplitude of the reproduction produced by the electromagnetic pick up device through the amplifier used therewith, the same to be connected to the windings id of the pick up by the lead connections indicated at 30. It will be noted also that the individual magnets I8 are magnetically attracted to the base II which forms a connection for the path of the magnetic flux out of the base 0f the magnet I8 toward the top of the sides of the frame. Moreover, it will be noted that the spring 24 is continuously exerting a pressure to maintain a firm magnetic contact between the bottom of the magnet l8 and the base II.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

What I claim is:

1. An insulating core and coil form carrying a coil and a plurality of permanent magnets with adjustable sleeve poles, said coil and magnets positioned in electrically inductive relation therebetween, said core having a plurality of substantially parallel openings extending transversely thereof; a plurality of permanent magnets, means to mount one magnet in each of said openings; a telescopic soft iron sleeve surrounding each magnet and substantially in contact therewith, each sleeve having a closed outer end and-being adjustably mounted in said transverse openings; means to retain said sleeve in various positions of adjustment relative to the coil form; a coil spring within said sleeve com pressed between the end of each magnet and the closed end of the sleeve; and means on the said sleeve for extending and retracting said sleeve.

2. An insulating core and coil form carryin a coil and a plurality of permanent magnets with adjustable sleeve poles, said coil and magnets positioned in electrically inductive relation therebetween, said core having a plurality of substantially parallel transverse openings therein; an imperforate magnetically permeable base member; a plurality of permanent magnets, means to mount one magnet in each of said openings; a telescopic soft iron sleeve centered with respect to and surrounding each magnet in sliding contact therewith, said sleeve having a closed outer end and being screw threaded into said transverse openings; a loaded spring within said sleeve interposed between the end of a magnet and the inside of the closed end of the sleeve; and means on the end of said sleeve for extending and retracting said sleeve relative to said coil form unit.

3. An insulating core and coil form carrying a coil and a plurality of permanent magnets with adjustable sleeve poles, said coil and magnets positioned in electrically inductive relation therebetween, said core having a plurality of substantially parallel transverse screw threaded openings therein; a peripheral recess around said form; a winding in said recess; an insulating member overlying said winding; an imperforate magnetically permeable base member; a plurality of permanent magnets, one mounted in each of said openings, said magnet resting on said base; a telescopic soft iron sleeve surrounding each magnet, said sleeve having a closed outer end and being screw threaded into said transverse openings; said overlying member having openings for receiving said sleeves; a coil spring within said sleeve compressed between the end of a magnet and the inside of the closed end of the sleeve; and meanson the end of said sleeve for extending and retracting said sleeve relative to said coil form unit.

4. In an electromagnetic pick up device, a boxlike metal frame magnetically permeable; an insulating coil form in said box, said form carrying a winding set in a recess in said form; a top insulating piece covering said form and winding; a plurality of holes through said piece and coil form for receiving individual magnets; a plurality of permanent magnets, means to mount one magnet in each of said openings; a telescopic soft iron sleeve surrounding and substantially in contact there with each magnet, said sleeve having a closed outer end and being screw threaded into said transverse openings; a coil spring within said sleeve compressed between the end of a magnet and the inside of the closed end of the sleeve; said winding, and said magnets with said conductive frame positioned in said coil form in electrically inductive relation; and means on the end of said sleeve for extending and retracting said sleeve relative to said coil form unit.

5. An insulating core and coil form, carrying a coil and a plurality of permanent magnets with adjustable sleeve poles, said coil and magnets positioned in electrically inductive relation therebetween, said core having a plurality of transverse screw threaded openings therein; a peripheral recess around said form; a Winding in said recess; an insulating member overyling said winding; an imperforate magnetically permeable base member; a plurality of cylindrically-shaped permanent magnets, one mounted in each of said openings, said magnet resting on said base; a telescopic soft iron sleeve surrounding said contacting each magnet, said sleeve being longer than said magnet and having a closed outer end, said sleeve being externally screw threaded to coact with the screw threads of said transverse openings in said coil form; said insulating overlying member having openings for receiving said sleeves; a coil spring within said. sleeve compressed between the end of a magnet and the inside of the closed end of the sleeve; and means on the end of said sleeve for extending and retracting said sleeve relative to said coil form-unit.

6. In an electromagnetic pick up device, a boxlike metal frame made of soft iron metal; an insulating coil form in said frame, said form having a recess therein; a winding located in said recess; a plurality of substantially paralleltransverse holes through said coil form for receiving individual magnets; a plurality of elongated cylindrically-shaped permanent magnets, one mounted in each of said openings and one end of each magnet in contact with the upper surface of the base of said soft iron frame; a telescopic soft iron sleeve surrounding each magnet, said sleeve having a closed outer end and being screw threaded into said transverse openings said winding, and said magnets with said conductive frame positioned in said coil form in electrically inductive relation; and a coil spring within said sleeve compressed between the end of a magnet and the closed end of a sleeve, said magnets being held in contact with said base by the combined force of the metallic flux and the pressure of said spring.

HARRY DE ARMOND.

REFERENCES CITED The following references are of record in the file of this patent:

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